The invention relates to a method of deriving information of the R.F. impedance presented by an electrical network at a port thereof, the network including a source of R.F. signals. The invention further relates to an arrangement for deriving such information.
The network may be the combination of an antenna and an antenna tuning unit, the antenna tuning unit having two ports one of which is connected to the antenna (which acts as the source of R.F. signals) and information being desired of the impedance presented by the combination at the other port; the invention may be used in matching the antenna to a radio receiver or transmitter.
Methods and arrangements for performing such matching are well known. For example, U.S. Pat. No. 3,919,644 describes an automatic antenna coupler for matching an antenna to a transmitter wherein the current and voltage components of signals in a line connecting the transmitter to a matching network and thence to the antenna are sensed by a pickup so as to detect the real part of the impedance or admittance presented to the transmitter and thereby to control the matching network: the signals in the line result from the R.F. energy supplied by the transmitter. U.K. Patent Specification No. 1,565,166, corresponding to U.S. Application Ser. No. 021,760, filed Mar. 19, 1979 now U.S. Pat. No. 4,283,794 describes a process wherein R.F. impedance information of a network is derived by injecting an R.F. current and an R.F. voltage with respective transducers and detecting resultant signals with a radio receiver: if the network is the combination of an antenna and an antenna tuning unit, this information may be used in matching the antenna to a radio receiver or transmitter.